Pressure controlled switch



March 10, 1936. B. w. DEZOTELL 2,033,417

PRESSURE CONTROLLED SWITCH Filed Aug. 7, 1934 1/ 1 III 11/ w I r Patented Mar. 10, 1936 UNITED STATES PRESSURE CONTROLLED SWITCH Bernard W. Dezotell, West Roxbury, Masa, as-

signor to United Electric Controls Company, Boston, Mass, a corporation of Massachusetts Application August 7, 1934, Serial No. 138,785

2 Claims.

The present-invention relates to pressure controlled switches, and more particularly to switches of this character designed for operation as limit controls to be actuated by the pressure within a heating system.

The purpose of the invention is to provide a simple, compact and accurate control of this type which may be inexpensively manufactured, and which is free from irregularities in operation.

With this and other objects in view, the various features of the invention consist in certain novel features of construction, combinations and arrangements of parts hereinafter described and claimed, the advantages of which will be obvious to those skilled in the art from the following description.

In the accompanying drawing illustrating the preferred form of the invention, Fig. 1 represents a section in elevation of the complete switch;

and Fig. 2 is a detail illustratingthe compensating mechanism for securing the desired differential in the operation of the switch.

Referring to the illustrated embodiment of the invention, the unit may be connected with the pressure space of the system through the threaded pipe connection Ill formed in the neck portion ii at the lower portion of the housing i4. Mounted above the neck i2 is a bellows i5, having a head i5 threaded at I8 into the neck portion and interiorly in communication through the here 20 with the pressure space. The joint between the head 56 and corresponding face of the neck i2 is sealed by a yielding washer ii to prevent entrance of steam into the space within the housing i4. Due to the fact that the interior of the bellows is subjected to variations in pressure, the unit is caused to expand and contract against the action of the loading spring 22. This movement of the pressure unit is caused to actuate a switch device through a stem 24 guided'on its upper end at 25. The guide 25 is in the form of a projecting web from a standard 28, which supports a self-contained switch unit 30 of the spring-type having an enclosing housing 32 and an operating pin 34 projecting through the housing for operation of the switch. The switch is pivotally connected to the standard It at 36 tor a purpose to be presently described.

The operating connection between the stem 24 and the pin 34 comprises a cylindrical housing 40 supported by an arm 42 to move with the stem 24, and containing a differential spring 46 interposed between an adjusting member 48 and an operating plunger 50. The operating plunger extends through the top of the housing into engagement with the pin 34, as indicated.

The sell-contained switch member pivotally mounted at 38 is normally maintained in contact with an adjustable abutment 52 through a bowed spring 54, as will be evident. Rotation of this abutment, which is mounted in an over hanging arm 56 on the standard 28, permits the operation of theswitch to be adjusted over difierent pressures, and constitutes a simple and efiec- 5 tive means for determining the pressure at which the device controls. 7 v

Aside from this, it is important in appaartus of this character that the switch after opening upon occurrence of excessive pressure, shall not 10 close too rapidly upon reduction of the pressure, or in other words, that there shall be a diiferential pressure lag between opening and closing movements of the switch. This differential lag is conveniently incorporated in the presentcon- 15 trol by virtue of the differential spring, which may be adjusted through the knurled nut 48 to cause any desired differential of operation up to a maximum of five pounds, approximately. It will be evident that by proper. adjustment of the 20 differential spring, the creation of premure suffi cient to open the switch unit will compress the spring. Thereafter, upon reduction of the pressure and contraction of the bellows, the differential spring will tend to maintain the switch open 25 for a suflicient period of time after contraction of the bellows to impose the desired operating difierential upon the switch unit itself.

As indicated in Fig. 1,. the standard 2% projects from a base member 58 to which the hous- 30 ing H is bolted, and the operating portions of the unit are surrounded by a cover member What is claimed is:-

1. A pressure controlled switchcomprising a bellows unit anchored at one end and subjected 35 to varying pressure, an operating member projecting from the free end of the unit, a completely housed switch unit pivoted adjacent one end, an operating pin projecting from the switch unit adjacent the opposite end, yielding connec- 40 tions between the operating member and pin, and means for adjusting the angular position of the switch unit about the fulcrum and in consequence the relation of the operating pin to the yielding connection. 45

2. A pressure switch comprising'a base membar, a housing member, pressure controlled bellows secured to the housing member and in free communication with the pressure space, a stem connected to the free end of the bellows extend- 50 with relation to the actuating connections to vary the operating range of the switch.

BERNARD W. DEZOTELL. 

